Something else to remember is that not everyone with insecure attachment problems experiences such intense feelings in therapy. Some insecurely attached people are more dismissive and others may have lesser degrees of attachment difficulties, so they may not experience the severely disruptive approach/withdraw conflict that is so characteristic of an unresolved attachment. I can look back at other close relationships I've had over the years and see the pattern very clearly now and I can see how disruptive it was in my life ever since I was very young. But if you attach to people more or less "normally" but with a bit of insecurity, then you may be able to deal with it relatively quickly in therapy.